Desert Pavements…Sturt Stony Desert

A desert pavement is a desert surface that is covered with closely packed, interlocking angular or rounded rock fragments of pebble and cobble size.

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Several theories have been proposed for their formation.[1] The more common theory is that they form by the gradual removal of the sand, dust and other fine grained material by the wind and intermittent rain leaving only the larger fragments behind. This does not continue indefinitely, however, because once the pavement has been formed it can act as a barrier to further erosion. Secondly, it has been proposed that desert pavement forms from the shrink/swell properties of the clay underneath the pavement; when precipitation is absorbed by clay it causes it to expand and later when it dries it cracks along planes of weakness. This geomorphic action is believed to have the ability to transport small pebbles to the surface over time; it stays this way due to the lack of abundant precipitation that would otherwise destroy the pavement development through transport of the clasts or excessive vegetative growth.

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http://en.wikipedia.org/wiki/Tirari-Sturt_stony_desert

The Tirari-Sturt stony desert ecoregion contains the gibber plains (desert pavement) and red sands of the large Sturt Stony Desert, the Tirari Desert to its southwest and the Flinders and Gawler Ranges to the south. The Tirari has more sand dunes than the Sturt Stony Desert and has also been the site of some important fossil findings. Towns of the ecoregion include the opal mining centre of Cooper Pedy, famous for its underground dwellings. the climate is very hot with summer temperatures reaching 50°C.

The region consists of the Stony Plains, Gawler, Flinders Lofty Block and the Broken Hill Complex bioregions of the Interim Biogeographic Regionalisation for Australia

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